In the prior art, the operation of a vehicle transmission is controlled by oil pressure. For example, in a belt type continuously variable transmission (CVT), torque capacity is adjusted by controlling the oil pressure supplied to a pulley. Torque capacity is the maximum torque which can be transmitted without causing the belt slip of the CVT. Tokkai-Hei 05-240331 published by the Japanese Patent Office in 1993 discloses a belt type CVT wherein, in a transient state where the accelerator pedal stroke (TVO) of the vehicle changes, or a speed change is performed, the oil pressure which adjusts torque capacity is controlled consistently.